Aluminium is one of the more demanding metals to bond well. As soon as it is machined or extruded, the surface reacts with air and forms a thin oxide layer within seconds. That layer bonds well to most adhesives, but it does not always bond well to the aluminium underneath it. This is why aluminium joints can fail at the oxide layer rather than at the glue line itself.Add in aluminium’s high thermal expansion rate, and any adhesive used across a temperature range needs enough flexibility to move with the substrate without breaking the bond.
The right adhesive for an aluminium job depends on three things: how much load the joint carries, whether it needs to flex with temperature change or vibration, and how the surface has been prepared. Get those three right and aluminium bonds as reliably as any other metal.
Below is a guide to choosing between adhesive types, followed by our full aluminium adhesive range.
Comparison table: adhesive types for aluminium
| Adhesive type |
Typical bond strength |
Cure time |
Flexibility |
Best suited to |
| Cyanoacrylate, also known as super glue |
Good for small areas |
Seconds to a few minutes |
Low — rigid once cured |
Small components, close-fitting parts, rapid assembly, and prototyping |
| Structural epoxy / MMA |
Very high |
10 minutes to several hours depending on grade |
Low to moderate |
Load-bearing joints, structural panel bonding, and applications needing maximum strength |
| Two-part polyurethane |
High |
20 minutes to a few hours |
Moderate to high |
Corner joints in aluminium window and door frames, and applications with some movement or differential expansion between substrates |
| Silicone / MS Polymer sealant-adhesive |
Moderate, not structural |
Skins in under an hour, full cure over 24–72 hours |
Very high |
Glazing, weatherproofing, and joints that need to accommodate ongoing movement |
Preparing aluminium for bonding
Surface preparation has more influence on aluminium bond strength than almost any other factor, and it is the step most often skipped or rushed on site.
Degrease first
Wipe the bond area with a solvent such as isopropyl alcohol or acetone to remove oils, release agents, and fingerprints. Aluminium extrusions in particular often carry a light film of manufacturing lubricant that will weaken adhesion if left in place.
Abrade the surface
A light key with an abrasive pad or fine sandpaper increases the surface area available to the adhesive and helps break through the outer oxide layer. Avoid heavy sanding that generates loose swarf, which needs to be cleaned off before bonding.
Clean again after abrading
Any dust or metal particles left on the surface will sit between the adhesive and the substrate and weaken the joint.
Bond within the recommended window
Aluminium starts re-oxidising as soon as it is cleaned. Most adhesive manufacturers recommend bonding within a few hours of surface preparation, some sooner. Check the technical data sheet for the product you are using.
Consider a primer or activator on demanding jobs
Some cyanoacrylate and structural adhesives perform noticeably better on aluminium with a compatible primer or surface activator, particularly on anodised or coated aluminium.
